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Currently, acoustic holography and beamforming are consolidated Noise Source Identification (NSI) techniques with expanding applications. These two microphone array based techniques can provide detailed sound field visualization. Even in enclosed space, such as a vehicle cabin, the sound field can be visualized using Spherical Harmonics Beamforming (SHB). Also, sound radiation from geometrically complex surfaces can be captured with conformal mapping using Statistically Optimized Near-field Acoustic Holography (SONAH). In this paper, an integrated approach using both techniques is presented as a manner to improve sound insulation during a vehicle development. Both vehicle and component level measurements are employed in order to identify the dominant sound transmission paths and add the appropriate acoustic treatments. It is shown that spherical beamforming and conformal mapping are powerful tools which expedite troubleshooting and allow vehicle acoustic content optimization.

Sound absorption materials can be key elements for mass-efficient vehicle noise control. They are utilized at multiple locations in the interior and one of the most important areas is the roof. At this location, the acoustic treatment typically comprises a headliner and an air gap up to the body sheet metal. The acoustic performance requirement for such a vehicle subsystem is normally a sound absorption curve. Based on headliner geometry and construction, the sound absorption curve shape can be adjusted to increase absorption in certain frequency ranges. In this paper an overall acoustic metric is developed to relate design parameters to an absorption curve shape which results in improved in-vehicle performance. This metric is based on sound absorption coefficient and articulation index. Johnson-Champoux-Allard equivalent fluid model and diffuse field equations are used. The results are validated using impedance tube measurements.